Pulling a worn out drill bit on an offshore drilling rig can take several days of continuous labor. The labor involved includes physically disconnecting connections between each of the tubing sections as the tubing is withdrawn until the drill bit is retrieved. The process must then be repeated to reinsert the new drill bit. Any improvement in tubing connections that can reduce the time it takes to disconnect or connect tubing sections can create significant cost savings by reducing the time required to complete the operation and get the new drill bit into operation.
One type of tubing connection is designed so that each tubing section can be connected to the next so that the exact orientation of the drill bit can be known in relation to the above ground tubing. Specifically, U.S. Pat. No. 5,950,744 (the '744 patent) discloses a pipe joint for self-aligning a drill string by means of “at least one downwardly projecting extension and a lower section having a corresponding recess for receiving the extension.” In the '744 patent a single downwardly projecting extension may only engage the corresponding recess in one orientation. In the '744 patent, multiple downwardly projecting extensions may also only mate with the corresponding recesses in one orientation because asymmetrical configurations are used for the multiple downwardly projecting extensions in order to ensure that the tubing may be connected in only one orientation.
The '744 patent solved the problem of finding a way to join together individual pieces of pipe, tubing, or casing so that an imaginary reference line will exist down the length of the drill string and, consequently, so that the operators at the surface will know the orientation of the drill bit at the bottom of the well bore. Prior to the invention of the '744 patent it was impossible to determine the orientation of the drill bit in threaded connections because the connection orientation differed from connection to connection depending on the tightness of the threaded connection. Additionally, the '744 patent solved the problem that threaded connections alone limit the rotation of the drill string to one direction. If the rotational direction of a threaded drill string is reversed, then the likelihood that at least one connection in the drill string will unthread is substantially increased. The splined connections comprising outwardly extending projections and corresponding receiving recesses disclosed in the '744 patent solve this problem because the splined connection strengthens the coupling and permits rotation clockwise or counterclockwise.
When a tubing connection can only be made in one orientation, time must be spent in rotating the tubing section to be connected until it aligns in the one position that will allow it to be joined. The amount of time spent in manipulating each tubing section to align it with the tubing section to which it is to be joined can be considerable when hundreds or thousands of connections are being made.
A need exists for an improvement to the '744 patent so that when it is not necessary to know the orientation of the tool at the bottom of the drill string, the pipe joint can permit alignment of the tubing sections in more than one orientation. Allowing alignment in more than one orientation will permit faster joining of the tubing sections and increase the strength of the coupling by increasing the number of splines.
A need related to connecting tubing sections in multiple orientations using splined connections, is the need to transmit electricity downhole to power electrical motors and other downhole devices such a choke. The downhole devices may be located at some point along the drill or tubing string, or they may be located at the end of the string of pipe. The need to transmit electricity is significant when using an electrical submersible pump (ESP) in an artifical lift method. A need also exists to transmit data from downhole sensors to surface operations through internally mounted wires in drilling operations and in production operations.
Basic artificial lift methods of producing oil and water from a well have improved and changed in recent years. Nearly all artificial lift methods still connect a plurality of pipes to form a conduit within a well that has been drilled and cased to allow oil and water to be pumped from the bottom of the well to production tanks at the surface. The production string usually has a pumping device at its lower end that is positioned near the bottom of the well bore that has been prepared for production. Pumping mechanisms such as electrical submersible pumps (ESP) and progressive cavity pumps (PCP) provide the energy needed to bring fluids to the surface through a string of jointed tubing. These pumps normally require an electric motor to function. Although many improvements have been made to these pumps over the years, there has been little done to reposition the wires that provide power to the pump from the outside of the tubing to the inside of the tubing.
For various reasons, those who are skilled in the science of producing fluids from a well have sought out a reliable method of supplying power to the bottom of a well bore. The previously proposed solutions to this problem have been unreliable, expensive, and complicated to install and remove. For example, the currently preferred power transmission method is to use bands to secure a cable that contains one or more wires to the outside of the production string of tubing. The bands keep the wire adjacent to the tubing so that it does not snag on the production casing or on any objects that might be in the well bore. The bands also support the cable's weight by securing the cable to the tubing. This method is problematic because it exposes the cable and bands to the corrosive elements of the well bore. Moreover, the odds of band failure increase during the installation (running) and removal (pulling) of the tubing in inclined well bores (the most common type of well bore) because the bands are more likely to hang at the gap where two joints of casing have been connected. Failure of one or more bands can prevent the removal of the pump or tubing because the annular space between the outside of the production tubing and the inside of the production casing is small and the cable, if not secured to the tubing, can wedge between the casing and the tubing causing the tubing to become stuck. Even if the cable does not break, the insulation on the wire inside the cable can be damaged which can create a short in the electrical circuit, rendering the wire essentially useless. The tubing string then has to be pulled back to the surface, and the short found and repaired before the pump can be run back to the bottom of the well bore. The problems created by banded external cables are costly and time consuming, and a reliable and cost effective alternative method of transmitting power from the surface to the bottom of the well bore is needed.
One solution to this problem is to use a plurality of tubing with multiple wires attached to the inside of the tubing instead of the outside of the drill pipe. While this solution alleviates the problem of snagging the wire or the bands, it does not solve the problem of exposing the wire to the harsh environment of the produced fluids that are contained within the production tubing. Simply hanging the cable on the inside of the tubing is also problematic because there is no way to support the cable's weight and the pump's pressure requirements will be higher because of the added friction between the fluid that is being pumped and the rough exterior of the cable.
Another solution to the above stated problem is to concentrically position the wires on the exterior of a tube that is inserted and attached to the actual production tubing itself. This solution avoids the problems presented by simply attaching the wire to either the interior or the exterior of the tubing. An example of this technique can be found in U.S. Pat. No. 4,683,944 (the '944 patent) entitled “Drill Pipes and Casings Utilizing Multi-Conduit Tubulars.” The '944 patent discloses a drill pipe with electrical wires positioned inside conduits in the drill pipe wall. But positioning the wire inside the drill pipe wall significantly decreases the overall pipe wall thickness. In order to overcome the decreased wall thickness, significantly thicker drill pipes would have to be used. The multiple conduits also create weak points in the drill pipe between the conduits. The high rotational stress that the drill pipe encounters in the drilling operations can cause stress fractures in the pipe wall between the multiple tubing conduits. In an extreme case, high rotational stress can lead to an internal fracture in the drill pipe that disengages the drill pipe's interior wall from its exterior wall.
Furthermore, manufacturing multiple conduit drill pipe is a complicated process, which is quite unlike the conventional drill pipe manufacturing process. Conventional drill pipe is manufactured by attaching male and female pipe connections to opposite ends of a conventional piece of pipe. The two connections are usually welded to the pipe. Multiple conduit pipes must be either extruded with the multiple conduits in place, or the multiple conduits must be drilled or cut out of a conventional drill pipe. In either case, the costs associated with manufacture of multiple conduit drill pipe are prohibitive.
Another problem encountered in the addition of wires to drill pipe, which is not unique to multiple conduits, is the problem associated with creating reliable, secure electrical connections. In conventional drill pipe, the individual pipe segments screw together, creating a problem for connecting the wires during the screwing or unscrewing process. This problem can be overcome by using drill pipe that plugs together and is secured with a threaded coupler. This type of connection is known in the art. The '944 patent discloses a similar type of coupling connection, but requires a planer conduit seal between the individual pipe segments in order to assure the integrity of the conduit connection. The removable conduit seal is crucial to the method in the '944 patent because a permanently installed conduit seal would be susceptible to damage during manufacture, transportation, storage, and installation of the multiple conduit drill pipe during drilling operations. Installing these conduit seals during the drilling process is also a cumbersome and a time consuming process. Therefore, a need exists for a method of transmitting electrical power to the bottom of a well bore in which the electrical connections are adequately protected from damage and the process of connecting the individual pipe segments is relatively simple and fast.
The prior art has previously attempted to supply power to the bottom of a well bore by alternative delivery methods as well. For example, in SPE/IADC article 798866 (the '866 article) entitled “Smart Drilling with Electric Drillstring™,” the authors disclose a method of supplying power to the bottom of a well bore using three separate ring connectors at each end of the tool joint. FIG. 1 is an illustration of the ring connectors 20 on the male end of the tool joint. As seen in FIG. 2, ring connectors 20 on the male end of the tool joint are positioned to mate up with ring connectors 21 in the female end of the tool joint when two pieces of pipe are mated together. Threading the tool joint together seals the electrical connection between the ring connectors. The use of ring connectors has the advantage that the pipe sections can be mated in any orientation. However, ring connectors have the disadvantage that frequent connection, disconnection, exposure, and reconnection of tool joints during the running and pulling process causes mud, dirt, and contaminants to become trapped between the ring connectors, that can cause an electrical short. Furthermore, the method disclosed in the '866 article is not preferable because wire 22, used to transmit power to the bottom of the well bore, makes two right-angle turns 24. Right angle turns 24 are not preferable because right angle turns 24 place excessive stress on wire 22 and substantially increase the likelihood of wire failure. Therefore, a need exits for an improved method of joining pipe together and supplying power to the bottom of a well bore that eliminates the need for ring connectors and that allows wire to run through the pipe in an approximate straight line without the need for any sharp angled turns in the path of wire.
U.S. Pat. No. 6,666,274 (the '274 patent) discloses a section of tubing with coupled end connectors and an insert containing at least one electrical wire. The insert has an outside diameter that is approximately equal to the inside diameter of the improved tubing. The insert also has projections at each end such that when two inserts are placed end to end, the projections will mate up. The insert has at least one groove cut into its side and running the length of the insert. The groove is for the placement of a wire for transmission of power to the well bore or for the placement of a wire for transmission of data from the well bore. The groove is installed down the length of the insert. The groove is deep enough so that when a wire is placed inside the groove, the wire does not project beyond the outside diameter of the insert. The insert may contain as many grooves and wire combinations as are necessary for the particular appiication. The wire has an electrical connection at each end of the insert. When the inserts are placed end to end, the insert projections line up the electrical connectors and correct mating of the insert projections will result in correct mating of the electrical connectors.
The inserts of the '274 application are the same length as the tubing and are installed inside the tubing such that the insert is flush with the first end of the tubing. The inserts are then welded to the tubing or secured to the tubing by some other method. A threaded coupler is then installed on the second end of the tubing to protect the exposed insert and electrical connector. The coupler will also be used to secure the improved tubing together. One of the methods disclosed by the '274 patent to solve the problem of aligning the electrical connectors for proper mating is the use of outwardly extending projections on one end and corresponding receiving recesses on the opposite end. (See FIGS. 10 through 14).
Persons skilled in the art are aware of various methods of protecting exposed wires within the tubing. For example, the article “Composite-lined Tubulars Can Lower Operating Expenses,” World Oil, July 2000, discloses fiberglass epoxy-lining, internal plastic coating and polyvinyl chloride and polyethylene coating. In the context of oil field applications the article states that “[l]ined tubulars consist mainly of steel tubing with standard oilfield connections lined with composites like glass-reinforced epoxy (GRE) or thermoplastic matrix materials such as high density polyethylene (HDPE) and polyvinyl chloride (PVC).”
As discussed above, a need exists for an improvement to the '744 patent to permit alignment of the tubing sections in more than one orientation. In addition, a need exists for an improvement to the '744 patent to allow the introduction of electrical wiring and connections. A further need exists for an improvement to both the '744 patent and the '274 patent so that the benefits of both inventions can be combined in one improved tool joint that allows connection in multiple orientations where the electrical connectors are in the tool joint itself and not in an insert. The needs identified above exist for production tubing, drill pipe, casing, and/or for any cylindrical pipe used to produce hydrocarbons in a subterranean environment.